Noncoherent Radar Pulse Compression Based on Complementary Sequences

Noncoherent pulse compression (NCPC), suggested recently, uses on-off keying (OOK) signals, obtained from Manchester coding a binary sequence with favorable a-periodic autocorrelation. This paper investigates the use of binary complementary pairs as a basis for NCPC. It shows that a pair of Manchester coded, N-element binary complementary sequences will yield a peak sidelobe (PSL) ratio of 1/(2N).     

Numerically Efficient Calculations of Clutter Map CFAR Performance

An alternative expression for the false alarm probability ofclutter map constant false alarm rate (CFAR), as derived by Nitzberg, is suggested. The new expression converges more rapidly.     

Removing autocorrelation sidelobes by overlaying orthogonal coding on any train of identical pulses

A coherent train of identical linear FM (LFM) pulses is used extensively in radar because of its good range and Doppler resolution. Its relatively high autocorrelation function (ACF) sidelobes are sometimes reduced through spectrum shaping (e.g., nonlinear FM, or intrapulse weighting on receive). We show how to completely remove most of the ACF sidelobes about the mainlobe peak, without any increase to the mainlobe width, by diversifying the pulses through overlaying them with orthonormal coding. A helpful byproduct of this design is reduced ACF recurrent lobes. The overlaid signal also results in reduced Doppler tolerance, which can be considered as a drawback for some applications. The method is applied to several trains of identical pulses (LFM and others) using several orthonormal codes. The effect on the three important properties of the radar signal: ACF, ambiguity function (AY), and frequency spectrum is presented. The effect on Doppler tolerance is studied, and implementation issues are discussed. The new design is also compared with complementary and sub-complementary pulse trains and is shown to be superior in many aspects.     

Detection loss due to interfering targets in ordered statisticsCFAR

The ordered-statistics (OS) constant false-alarm rate (CFAR) is relatively immune to the presence of interfering targets among the reference cells used to determine the average background. OS CFAR performance in a multitarget environment was previously studied by simulation. The author obtains analytic expressions for the added detection loss, assuming strong interfering targets. The real target is assumed to be a Rayleigh fluctuating target. Numerical examples are included     

Theoretical Bounds on Random Errors in Satellite Doppler Navigation

Analytic expressions of the random errors in a satellite Doppler navigation system are developed. The errors in the along-track and across-track coordinates are expressed as functions of the geometry (range and angle), pass-length, and signal-to-noise ratio (SNR). Such an analytic result becomes possible due to an explicit solution to a simplified rectilinear model of the satellite pass over a flat Earth. It is shown that the explicit solution performance in the presence of noise is identical to that of the iterative solution, used in the real navigation problem.     

Angle-Independent Doppler Velocity Measurement

When the angle between the target heading and the range vector is not known a priori, a Doppler velocity radar must estimate them simultaneously by utilizing a longer section of the track. The conventional least squares iterative solution is compared with a new explicit alogorithm which utilizes range-rate derivatives. It is shown that the explicit algorithm is biased but is less sensitive to noise. The bias, however, can be estimated and removed. Hence, the computationally simpler explicit velocity estimation method yields better performance. An analytical closed form expression for the resulting mean square estimation error and simulation results are given.     

Performances of order statistics CFAR

A previous analysis of order-statistics constant-false-alarm-rate (OS-CFAR) radar receiving a single pulse from a Rayleigh fluctuating target in a Rayleigh background is extended to a Rayleigh-plus-dominant target. The analysis includes effects of a multitarget environment. A detailed comparison of OS-CFAR, cell-averaging (CA) CFAR, and censored CA-CFAR is provided for a Rayleigh target in the presence of strongly interfering targets. The false-alarm analysis of OS-CFAR is extended to the more general case of a Weibull background. The deterioration of the CFAR property of OS as the shape factor, C, of a Weibull probability density function changes from Rayleigh (C=2) to a longer-tailed one (C<2) is evaluated. The analytic comparison between CA-CFAR and OS-CFAR is extended to an integration of pulses reflected from a Swerling II target. The OS-CFAR performance (with and without interfering targets) yields an integral equation that is solved numerically     

Passive Array Tracking of a Continuous Wave Transmitting Projectile

Differential Doppler measurements by a passive array are used to track an unstable continuous wave (CW) source moving in a ballistic trajectory, e.g., a projectile carrying a proximity fuse. The ballistic equations of motion couple frequency measurements at various sections along the track with the track parameters at any arbitrary time, e.g., at impact. A nonlinear weighted leastsquare method is used to estimate the track parameters, and the resulting error covariance matrix is derived. A numerical example demonstrates the relative contributions of various frequency measurements to the estimation accuracy.     

Upgrading conical scan with off-boresight measurements

Adding off-boresight measurements to a conical scan radar can bring the angle accuracy closer to the theoretical attainable limit. A model for off-boresight measurement implementation and its performances are discussed. The expected accuracy is calculated and compared with the Cramer-Rao bound. The model is also used to determine bias error induced by the target dynamics.     

Family of multicarrier bi-phase radar signals represented by ternary arrays

A K times L ternary array, comprised of the elements {0, 1, - 1}, with some unique features, represents a multicarrier radar signal with favorable autocorrelation and ambiguity functions. Constructing such an array using Galois fields is described. As in a Costas binary array, only one frequency is transmitted at any time slot, but in our array the same frequency is repeated in several time slots, yielding a signal with considerably larger pulse compression than a Costas signal that uses the same number of frequencies